【求助】TPO3阅读8/14，正确答案和文章意思有出入么？

唱什么歌

请帮我看看：
Q：What does the author imply about modern architectures in Paragragh 4?
A:They weigh less in relation to their size than buildings constructed 100 years ago.
这个选项中in relation to 的意思如何理解？
是不是由于建筑物size的原因，现代建筑轻了？

定位到原文是：
Progress in this area can be measured by the difference in weight between buildings built now and those of comparable size built one hundred years ago.
意思是对相同大小的建筑物而言，现代建筑更轻。

原文第四段其他地方好像也没有出现答案的可能了。
这个正确答案和原文是不是有出入了？
请赐教~